29 AUSTRALIAN FIELD ORNITHOLOGY 2005, 22, 29-37 Historical Records of the Powerful Owl Ninox strenua in and Comments on the Species' Status

IAN A.W. McALLAN1 and DARIEL LARKINS2

146 Yeramba Street, Turramurra, 2074 2225 Kissing Point Road, Turramurra, New South Wales 2074

Summary The Powerful Owl Ninox strenua is now regularly reported in the Sydney area, New South Wales, though there were few records before the 1970s. Questions have arisen as to whether the population has grown in number or whether the species was previously overlooked. Historical records of the Owl for the Sydney area and changes in its local abundance are considered. Evidence for an increased population in parts of Sydney is given.

Introduction Recently, Kavanagh (2004) assessed the status of the Powerful Owl Ninox strenua in the Sydney area of New South Wales. It was thought that although the species is now recorded more frequently, this may be related to a greater awareness of the species among birdwatchers and an increased knowledge of owl survey techniques. At the same time, Kavanagh pointed out that changed fire regimes and nutrification of urban bushland may have benefitted the Common Ringtail Possum Pseudocheirus peregrinus, a preferred prey species of the Powerful Owl. This paper re-examines the long-term records of the species in Sydney, particularly in the northern suburbs where we have almost 65 years' combined experience of · birdwatching.

Status in Sydney up to the 1950s When the Sydney area was first settled by Europeans in the 18th century, the Powerful Owl was evidently a rare species. Over 150 species of birds were illustrated in watercolour paintings made at this time by various artists (Mathews & Iredale 1920; Hindwood 1964, 1965a,b, 1970). These paintings included images of species that have been considered rare locally for most of the last 100 years, such as the Red Goshawk Erythrotriorchis radiatus, Red-tailed Black-Cockatoo Calyptorhynchus banksii, Ground Parrot Pezoporus wallicus, Eastern Bristlebird Dasyornis brachypterus and Blue-faced Honeyeater Entomyzon cyanotis (McAllan 2002). Nocturnal birds pictured include the Barking Owl Ninox connivens, Southern BoobookN novaeseelandiae, Masked Owl Tyto novaehollandiae, Barn Owl T. alba, Tawny Frogmouth Podargus strigoides and Australian Owlet-nightjar Aegotheles cristatus. There appears to be no such illustration of the Powerful Owl. George Caley arrived in Sydney in 1800 and spent the following decade collecting birds near Sydney and . He recorded the Southern Boobook, Barn Owl, Tawny Frogmouth, White-throated Nightjar Eurostopodus mystacalis and Australian Owlet-nightjar but fai led to record the Powerful Owl (Vigors & Horsfield 1827). Although the early paintings and Caley's records are in themselves not an indication of rarity, they suggest that other species currently perceived as rare in Sydney, such as the Red Goshawk, Ground Parrot, Barking Owl, Masked Owl and White-throated Nightjar, were then more noticeable than the Powerful Owl. AUSTRALIAN 30 McALLAN & LARKJNS FIELD ORNITHOLOGY

By the time that John Gould scientifically described the Powerful Owl in 1838, the European settlers had explored much of coastal south-eastern (Gould 1838, Feeken et al. 1970). It is not known where Gould's specimen of the Powerful Owl was collected. However, Charles and Stephen Coxen, Gould's brothers-in­ law, were based at Yarrundi, west of Scone in the upper Hunter River valley, and supplied Gould with many specimens before he arrived in the Colony (Sauer 1982). Gould himself collected a Powerful Owl in the Liverpool Range near Yarrundi on 27 October 1839 (Gould drafts to his Birds ofAustralia in Cambridge University Library, UK; Gould 1865). Presumably this was at Cedar Brush which was visited by Gould on several occasions and where the species can still be found (Gould 1865; IMcA pers. obs., 21 May 1987; T Jurd in Stuart 1994, 1995). The earliest record known of the Powerful Owl near Sydney is a bird collected at Macquarie Fields on the in early September 1875 (Edward P. Ramsay diaries, Mitchell Library, State Library of NSW; also Ramsay 1890). This specimen was given to Ramsay, the then newly appointed Curator of the Australian Museum, and evidently passed to Ramsay's family collection, known as the Dobroyde Collection. A specimen from Macquarie Fields was registered into the Australian Museum with the rest of the Dobroyde Collection in 1912 (AM 0 .18275). Later Sydney specimens from the 19th century include one collected at Campbelltown and registered into the Australian Museum collection in May 1880 (AM A.8189), and another from Smithfield registered in June 1893 (AM 0.6202). In the 1890s A.J. North considered the Powerful Owl rare in Sydney, noting records from 'the thick scrubs of the Hawkesbury district and about George's River' (North 1898). He went on to observe that 'one of these birds, shot at Richmond, had an opossum in its claws'. The species was noted at in late 1925 and 1926 and there were occasional sightings in the Park through to the 1960s (K.A. Hindwood Bird Recording Service, Mitchell Library [hereafter KAHBRS]; Debus & Chafer 1994). Nonetheless, the species was perceived to be rare in metropolitan Sydney for many decades until at least as late as the 1950s (Hindwood & McGill 1958).

Status in Sydney since 1950 The first record of which we are aware for the northern suburbs of Sydney was a bird seen by Norman Fearnley, H. Salmon and Keith Hindwood at West Pennant Hills on 6 November 1955 (KAHBRS, Debus & Chafer 1994). We have also been told of an undated sighting in the 1950s at the Blue Gum Creek valley in West Chatswood by Richard Geraghty (A Burton pers. comm.). However, the Powerful Owl was not recorded in this area by Keith Hindwood who also lived in West Chatswood in the 1940s and 1950s. There were further records at Elouera Bushland Reserve (now Berowra Valley Bushland Park) near Thornleigh and High Ridge Creek in Gordon in 1959, at Bayview and Lindfield in 1962 and at Normanhurst in 1969 (P.E. Roberts pers. comm.; KAHBRS; Debus & Chafer 1994). The sightings at Gordon Creek at Lindfield in 1962 included a pair and a young bird, evidence of breeding in the Catchment at this time (Jack Waterhouse in KAHBRS). Although it could be said that the local observers were inexperienced with the species, there were already many capable birdwatchers in the northern suburbs at this time, including Robin Bigg, Dick Cooper, Lawrie Courtney-Haines, Molly Crawford, Stephen Debus, Keith Hindwood, Ern Hoskin, Barbara Howie, S.G. (Bill) Lane, Richard Noske, Jack Purnell, Peter Roberts, Alan Rogers, and Tony VOL. 22 (1) MARCH 2005 Historical Records of the Powerful Owl 31

Rose. In addition, DL has been resident in South Turramurra since 1956. Most of these observers did not record the species locally, even though by the late 1960s field-guides were correctly describing the typical woo-hoo call of the species (e.g. Cayley 1968), and this call was described in the ornithological literature more than 20 years before (Fleay 1944). As there were few records in the northern suburbs, despite the presence of many experienced observers, we believe that, although the Powerful Owl was present, it was genuinely rare locally through to the end of the 1960s. Such a belief is also held today by some of these residents of the 1960s (e.g. Dick Cooper, Stephen Debus, Peter Roberts and Alan Rogers). During the 1970s and early 1980s the Powerful Owl was occasionally reported in Ku-ring-gai Chase National Park, with records from North Wahroonga, Bobbin Head, Appletree Bay and (A.B. Rose & P.E. Roberts pers. comm.). Young birds were occasionally seen, and it is likely that the species was then breeding in Ku-ring-gai Chase to the north of these suburbs. DI.:s first record of the Powerful Owl was in April 1971 when a bird called repeatedly at her home in South Turramurra. DI.:s residence is on a ridge dominated by 25-m-tall Blackbutts Eucalyptus pilularis. This locality was subsequently found to be 2 km east of a breeding site in the valley in Pennant Hills Park. DL heard Powerful Owls at least twice over the next two months, usually not long before first light. Duetting birds were believed to have been heard on at least one of these occasions. DL heard Powerful Owls a further seven times during 1972 and 1973. They were not heard in 1974; however, DL heard a single bird calling in May 1975. On 19 November 1977 two Powerful Owls were found by Trevor Allan and Brian Larkins at Scout Camp Creek in Pennant Hills Park. These observers had explored most of the bushland area of the upper over the previous 20 years. One of the birds seen on this occasion was an immature first-year bird. A single bird was observed at this locality by Brian Larkins and DL the following week. DL heard the Powerful Owl again in January 1980, but on no other occasion in the 1980s. In the early 1980s a regular roosting site was discovered by John Seale at Devlins Creek in Pennant Hills Park, over the ridge from the roosting site found by Trevor Allan and Brian Larkins in 1977 (J. Seale pers. comm., who showed IMcA the site on 26 May 1985). This Devlins Creek site was independently discovered by C. (Sandy) Sansom on 2 December 1990 (Sansom 1991). A tree with a breeding hollow was subsequently found elsewhere in the Devlin's Creek valley (Kavanagh 2004). Records of the Powerful Owl at the roost-site have been made by many birdwatchers ever since. During the 1990s the number of reports for elsewhere in the Lane Cove River valley gradually increased. IMcA first heard the species at his residence, in a valley 2.5 km east-north-east of the Devlins Creek roost, on 28 March 1994. He had heard the species in the wild elsewhere in 1987 and knew the call from tapes since at least 1981. Both the authors have heard the Powerful Owl at home on many occasions since 1994 (Figure 1). None of these observations was elicited by the call-playback technique or spotlighting, and often the observations involved the observers being woken by the calls. No calls were heard by both authors on the same night, even though the two localities are less than a kilometre apart. Debus (1995) suggested that Powerful Owl calls carry to 1.5 km. We suspect that this disparity is because of the majority of the calls being heard indoors and loud enough to wake the authors. The distance that calls carry may vary with wind speed and direction and AUSTRALIAN 32 McALLAN & LARKINS FIELD ORNITHOLOGY

25

20

15 No. of records 10

0 1970- 1975- 1980- 1985- 1990- 1995- 2000- 1974 1979 1984 1989 1994 1999 2004 Years Figure L Records of Powerful Owl calls heard at the authors' homes in Thrramurra, northern suburbs of Sydney, from 1970 to September 2004. other meteorological conditions, as well as vegetation type, but in this instance a high ridge separates the two localities and this may have deflected some of the calls. As no calls were heard by both authors on the same night, it is likely that most calls were from birds less than 500 m from the two residences. Calls were heard in all months except December, with more records from late summer and early autumn (Figure 2). This pattern supports the findings of Fleay (1968), Hollands (1991) and Debus (1995), who recorded the calls more frequently between February and June than in other months. The Powerful Owls recorded by DL in the early 1970s were heard for only a limited period between April 1971 and April 1973. It is possible that they hunted locally until there were few prey animals left and then exploited other parts of their territory. Such activity was suggested by Kavanagh (1988, 1992), Chafer (1992) and McNabb (1996) for predation on populations ofthe Greater Glider Petauroides volans and the Common Ringtail Possum. Traill (1993) noted reductions in Squirrel Glider Petaurus nO!folcensis numbers under sustained Powerful Owl predation, though the Owls themselves did not leave the area during the study. DL has known the calls of the Powerful Owl since the early 1970s and IMcA from the early 1980s. Our records show that there has been an increase in the calling rate locally. Apart from the records from the early 1970s, the authors heard few birds at home before the 1990s. Alan Rogers has also observed a similar

7 6 5 No. of 4 records 3 2

0 J F M A M J J A S 0 N D Month Figure 2. Records of calls of Powerful Owls by month, Thrramurra. VOL. 22 (1) MARCH 2005 Historical Records of the Powerful Owl 33 increase in calling of the Powerful Owl at Westleigh, 4 km north-west of the Devlins Creek site. He first heard the call locally in April 1985, with only two further records of calls over the next decade. The number of records increased in the late 1990s with at least 16 records of calling birds since September 2000 (A Rogers pers. comm.). The first documented record in the Lane Cove River valley below Fullers Bridge is a single bird at Riverview College some time between 1968 and 1980 (Dixon 1982). The next record for the lower valley was at least nine years later when a bird was heard calling in the deep valley below Gore HiJI at Lane Cove (I. Campbell in Morris & Burton 1992). The numbers of records from the lower Lane Cove River valley have since increased and the species is now regularly recorded from suburbs along the foreshore (Kavanagh 2004). Some increase has also occurred in the species' range in the southern suburbs of Sydney, with recent records from north of the Georges River at Lugarno and Brighton-le-Sands (R. Stokes andP. Straw in Morris 2001). These birds presumably originated from the populations in the and River catchments.

Discussion Kavanagh (2004) suggested that changes in the status of the Powerful Owl in Sydney between the first National Atlas run by the Royal Australasian Ornithologists Union from 1977-1981 (19 records) and the second from 1998- 2002 (138 records) may have been related to an increased awareness of the species amongst ornithologists as well as an increased knowledge of owl-survey methods. However, direct comparisons between the Atlases are problematic. In the first Atlas observers were asked to submit record sheets of data collected in areas measuring 10 minutes latitude by 10 minutes longitude. Observers were encouraged to collect data at a seasonal level, i.e. over three-month periods (Blakers et al. 1984). In the second Atlas observers were encouraged to submit point data over 20-minute counts and to revisit these localities regularly, submitting new record sheets each time (Barrett et al. 2003). With these differences it is not surprising that there were more Sydney records in the second Atlas. At the same time the statistics presented in the two Atlases suggest that there was a decline in reporting rate from the 11-40% category to less than 10% (Blakers et al. 1984, Barrett et al. 2003). This apparent anomaly is because of a much larger number of short species lists in the second Atlas, resulting in a bias towards easily observed and common species. Kavanagh's map suggests that there has been an increase in the Owl's range through Sydney in recent decades (Kavanagh 2004). However, there is no evidence that this change in range has anything to do with owl-survey methods. Our observations indicate an increase in unelicited calling by the Powerful Owl in South Turramurra. This has apparently occurred elsewhere in the northern suburbs, as long-term-resident Sydney birdwatchers to whom we have spoken, e.g. Peter Roberts at Mt Kuring-gai and East Lindfield, and Alan Rogers at Westleigh, also consider the species to now be more common. Observers contacted who previously lived in Sydney in the 1960s and 1970s e.g. Dick Cooper (Hornsby) and Stephen Debus (Longueville) but now live elsewhere, also considered that the Powerful Owl was rare in the northern suburbs at that time. AUSTRALIAN 34 McALLAN & LARKINS FIELD ORNITHOLOGY

Since the discovery of the breeding tree in 1991, adults with young have been regularly observed at both the Devlins Creek and Scout Camp Creek roosts. Kavanagh recorded 14 young Owls fledging from the Devlins Creek nest-tree from 1990 to 2002 (Kavanagh 2004). Allan's and Larkins's record of a young bird not far from the Devlins Creek roost in November 1977 suggests that the Powerful Owl has been breeding in the locality from at least that time. The number of young produced in this area is likely to be in excess of 30 birds. Dispersal of the young to set up territories elsewhere is likely to result in a continuing increase in the population as long as food, breeding hollows and territories are available. The Powerful Owl is now found in most of the northern suburbs, as well as in the southern suburbs adjoining Royal National Park and the lower Georges River (Kavanagh 2004). It has been recorded irregularly in Royal National Park since 1925, which suggests that there has long been a core population in the area centred on the rainforests and tall eucalpt forests of the Hacking and valleys. Similarly, the 1950s and 1960s records from West Pennant Hills and Normanhurst suggest that there may have always been pairs in undisturbed vegetation in the valley and Ku-ring-gai Chase National Park. Pairs are now known to breed in most of the larger areas of urban bushland including Berowra Valley Bushland Park, , the Lane Cove River valley and Middle Harbour (Kavanagh 2004). Kavanagh (2004) noted that in recent years Powerful Owls have been recorded in areas surrounding Port Jackson proper and occasionally in the eastern suburbs. Many of these localities are close to the homes of birdwatchers who were resident during the 1960s and 1970s, but did not record the species locally (e.g. Robin Bigg, Stephen Debus, David James and Bill Lane). Sightings continue to be made in areas with little original vegetation or areas with high human disturbance such as the Royal Botanic Gardens (Kavanagh 2004; A. Leishman pers. comm.). IMcA has seen Powerful Owls at localities as disturbed as the crowded concourse of Circular Quay in the Sydney Central Business District (7 December 2002) and in a spotlit tree adjacent to an Olympic pool filled with patrons at Hornsby (17 July 1996). This apparent change in status may have come about through many causes. These include: a reduction in persecution of the Owl by humans; a reduction in the number of cats Felis catus, dogs Canis lupus and Foxes Vulpes vulpes; an increase in the abundance of preferred prey species; and reduced fire frequencies and the nutrification of urban bushland. Supervision of cats and dogs and their night-time restraint is greater than in the past and much of this change has been related to trends in society rather than any other reason. Baiting programs for Foxes in urban bushland areas may also have had an effect on the numbers of stray dogs, which are susceptible to 1080 poison. In the years from the 1950s to the 1980s the most commonly observed possum was the Common Brushtail Possum Trichosurus vulpecula (DL & IMcA pers. obs.). The Common Ringtail Possum was also present, as well as the Sugar Glider Petaurus breviceps. However, both were in lower numbers than the Common Brush tail Possum and were possibly kept in check by cats and dogs. Until the late 1990s it was a common practice in Sydney for 'nuisance' Common Brushtail Possums in urban areas to be trapped and moved to areas of bushland (Mathews et al. 2004). This may have reduced Common Brushtail Possum numbers in some areas with the niche being partially filled by the Common Ringtail Possum. Kavanagh (2004) suggested that a reduced fire frequency in the gullies of urban bushland and nutrification of these gullies through urban runoff may have resulted VOL. 22 (1) MARCH 2005 Historical Records of the Powerful Owl 35

in an increased structural complexity of the forest and an increase in preferred food plants for the Common Ringtail Possum, allowing the Possum to increase its population. Nutrification, with associated weed growth such as privets Ligustmm spp., Lantana Lantana camara and Camphor Laurel Cinnamomum camphora, has certainly occurred in the Lane Cove River valley (Martyn 1994 ). This probably accelerated with an increase in urban population and associated increases in disturbance of the original vegetation, such as the construction of sewage pipelines through the valley from the late 1950s to the late 1960s. An overall reduced fire frequency in some parts of Sydney has resulted in an increase of endemic mesomorphic species such as Sweet Pittosporum Pittospomm undulatum, Cheese Tree Glochidion ferdinandi and Blueberry Ash Elaeocarpus reticulatus (Benson & Howell 1990, 1994). During the 1960s and 1970s there were major fires in the upper Lane Cove River valley in 1961, 1964, 1970 and 1976 (DL & IMcA pers. obs.). However, there were few prescribed control burns from 1956 through to January 1994 when much of the bushland of the upper valley was burnt by fires (Martyn 1994). This fire, as well as another in January 2002, included parts of the Devlins Creek valley, adjacent to and beneath the Owls' breeding tree (!MeA & DL pers. obs.). Prescribed control burns within the valley increased markedly following the 1994 fire, but the Powerful Owls have continued to rear chicks in the Devlins Creek valley since the discovery of the nest-tree in 1991, including in 1994 and 2002 (Kavanagh 2004). Land use within the Lane Cove River valley itself has changed significantly since the 1950s. In those days farming was widespread in the valley and surrounding areas, including dairies in West Chatswood, and orchards, intensive horticulture and poultry farms in South Turramurra, North Epping and the future site of Macquarie University. Logging for timber also occurred in parts of the valley through to the late 1950s. These activities, which involved widespread clearing and often removal of the remaining understorey, were evidently not as advantageous for the Powerful Owl and its prey as is current usage of suburbs with parks and gardens. It could be that the planted trees and shrubs and weeds within the suburbs have matured and are able to support a larger population of the Common Ringtail Possum. This may mean that the Powerful Owl is now able to forage in the suburbs more effectively. For whatever reason, the Common Ringtail Possum can now be seen in many parts of suburban Sydney (IMcA & DL pers. obs.). The Common Brushtail Possum is still found, though at present in lower numbers than in the 1960s and 1970s, whereas the Sugar Glider remains rare. Spotlighting and observation by IMcA in June and July 2004 in the upper Lane Cove River valley found the Common Ringtail Possum abundant within the suburb of South Turramurra but rare in surrounding bushland. It is worth noting that in a study of Powerful Owl diet at Mt Coot-tha in Brisbane, Qld, Pavey et al. (1994) considered that most of the Common Ringtail Possums eaten were taken in surrounding suburbs and not in the reserve itself where the Possum was not recorded. Other changes in wildlife populations will have benefitted the Powerful Owl. We have recorded the Sulphur-crested Cockatoo Cacatua gale1ita, Crimson Rosella Platycercus elegans and Pied Currawong Strepera graculina amongst the prey of Powerful Owls several times, both as incidental records and as remains at the Devlins Creek roost. Kavanagh (2004) also recorded the Pied Currawong, Crimson Rosella and Rainbow Lorikeet Trichoglossus haematodus regularly in the diet of AUSTRALIAN 36 McALLAN & LARKINS FIELD ORNITHOLOGY the Powerful Owl in the Sydney area. Moreover, he found birds more frequently in the diet of both the Powerful Owl and the Masked Owl on sites on the Central Coast of New South Wal es than at sites in the south-east (Kavanagh 2002). Kavanagh suggested that birds may be taken more frequently by Powerful Owls living in bushland fragmented by urban and rural developments where arboreal marsupials may often be less abundant. In Sydney the Sulphur-crested Cockatoo, Rainbow Lorikeet and Pied Currawong have increased significantly in number since the 1950s (Hoskin 1991 ). There has also been a significant increase in the Crimson Rosella population in some northern suburbs of Sydney. In the mid 1970s this species was outnumbered by the Eastern Rosella Platycercus eximius in a ratio of perhaps five to one (IMcA & DL pers. obs.), but the reverse is now the case. Again this may have been caused by changes to the density of the vegetation in the suburbs and surrounding bushland. Records of unelicited calls of the Powerful Owl heard by the authors and other observers have increased markedly in the last 20 years. Increased calling, coupled with an increasing range of the species in metropolitan Sydney, leads us to believe that the Powerful Owl has become more common and adapts well to the urban environment.

Acknowledgements The following helped greatly with their recollections of the Powerful Owl in the Sydney area and by providing info rmation on other aspects of the paper: Andy Burton, Dick Cooper, Stephen Debus, Gary Dunnett, Rod Kavanagh, David James, Alan Leishman, Marie McAIIan, Peter Roberts, Alan Rogers, Tony Rose and John Seale. Advice was also received from an anonymous referee. Staff at the Mitchell Library, State Library of New South Wales, helped with access to the E.P. Ramsay diaries and the K.A. Hindwood Bird Recording Service. Ern Hoskin allowed access to these files before they were donated to the Mitchell Library. Assistance was also received from the staff of the Cambridge University Library, Cambridge, UK, on a visit by IMcA in 1994.

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Received 13 May 2004 •